Cavity Wall Construction (Hansard, 12 November 1974)

§ Mr. Kilfedder
asked the Secretary of State for Northern Ireland what are the present values of thermal insulation that can be achieved by the different forms of cavity wall construction; and how far the requirements of building standard regulations take account of the saving in energy consumption which can be achieved by the use of modern insulating materials.

§ Mr. Concannon
The following examples illustrate the values of thermal insulation achieved by three of the most common forms of cavity wall construction. The standard unit used for measuring thermal insulation is watts per square metre per degree centigrade.

105 mm brick outer and inner leaves with 16 mm dense plaster on inside face 1.5 units

105 mm brick outer leaf, 100 mm lightweight concrete block inner leaf and 16 mm dense plaster on inside face 0.96 units

75 mm aerated concrete block outer leaf rendered externally, 100 mm aerated concrete block inner leaf with 16 mm leaf with 16 mm plaster on inside face 0.84 units

The Northern Ireland building regulations prescribe standards for structural stability, thermal insulation and the prevention of penetration of moisture and spread of fire. They require the external wall of a dwelling to be constructed so that the thermal transmittance coefficient is not more than 1.70 units. Most forms of cavity wall construction in common use will therefore comply without the use of any additional insulating material.

§ Mr. Kilfedder
asked the Secretary of State for Northern Ireland how many houses have been built in Northern Ireland where the brick/cavity/brick wall method has not been used; whether, and on what grounds, this type of construction is approved; and if he will make a statement.

§ Mr. Concannon
The information requested is not readily available and could not be provided without disproportionate use of resources.
The object of new building techniques, many of which do not use brick/cavity/ brick walls, is to increase the rate of 112W building and to make the best use of scarce resources.
In all cases the construction of external walls of dwellings must satisfy the conditions prescribed in the building regulations. These regulations do not specify the method of construction but prescribe standards of structural stability, thermal insulation, and the penetration of moisture and spread of fire. Any method of construction which meets these standards may be approved.

105 mm brick outer and inner leaves with 16 mm dense plaster on inside face	1.5 units
105 mm brick outer leaf, 100 mm lightweight concrete block inner leaf and 16 mm dense plaster on inside face	0.96 units
75 mm aerated concrete block outer leaf rendered externally, 100 mm aerated concrete block inner leaf with 16 mm leaf with 16 mm plaster on inside face	0.84 units